Power-operated impact wrench



P 1951 F. T. HAMLIN 2,566,661

POWER-OPERATED IMPACT WRENCH Filed Oct. 9, 1948 21 i 'gh 40 3 as h d 4425 an 22 I9 39 4 2G l5 lNVENTOR FREDE RIG T. HAMLIN.

HIS ATTORNEY Patented Sept. 4, 1951 POWER-OPERATED IMPACT WRENCHFrederic T. Hamlin, Stewartsville, N. J., assignor to Ingersoll-RandCompany, New York, N. Y., a corporation of New Jersey ApplicationOctober 9, 1948, Serial No. 53,620

5 Claims.

This invention relates to impact wrenches and more particularly towrenches utilized to rotate relatively large nuts, as for example,around 5 inches outside diameter.

Heretofore, in order to tighten or loosen nuts of the size referred to,it was necessary to resort to the wrench sledge hammer method or, inlieu of a sledge hammer, a ram supported from the ceiling by cables orropes and swung back and forth by two or more men was used to hammer thewrench. Such an arrangement has several obvious disadvantages, otherthan its inefficiency-as for example, the high linear stressesdevelopedin the bolt on which the nut is being tightened. It is,accordingly, one object of my invention to develop torque free of linearstresses for tightening nuts and bolts and the like.

Another object of my invention is to utilize the rotational energy of abody, relatively massive compared to the body to be rotated, in a deviceof the character referred to.

A further object of my invention is to construct an impact wrench insuch a manner that the driving force or prime mover for the wrench isnot subject to undue strain at the instant of impact of the wrench.

Other objects will become obvious hereinafter.

In the drawing accompanying the specification and in which similarreference characters refer to similar parts,

Figure l is a vertical elevation, partly in section, of an impact wrenchconstructed in accordance with the practice of the invention,

Figure 2 is a top view, partly in section, of the impact wrench arrangedto rotate a body in the clockwise direction.

Figure 3 is a top view of the impact wrench arranged to rotate a body inthe counterclockwise direction, and

Figure 4 is a vertical elevation, partly in section, of the clutcharrangement for the impact wrench for obtaining counterclockwiserotation of the body to be rotated.

Referring to the drawing and more particularly to Figure 1, ldesignates, in general, a preferred form of the impact wrench supportedin its operative position for tightening a nut II on a bolt 12 by acradle I! which in turn is supported by cables 20 depending from anoverhead construction (not shown). In the main, the wrench l0 comprisesa torque producing member or wheel l3 of relatively massive size,compared to the nut II, rotated by an air motor l4 slidably mounted on awrench member l which intermittently engages the wheel 13 to transmittorque therefrom to the nut H. To this end, the wrench member 15 at oneend grips the nut II and is provided on the other, or opposite, end witha pair of cams it having engaging faces I! spaced degrees apart andpositioned coaxially with a similar pair of cams [8 on the wheel l3 forengagement therewith.

More specifically, the cradle l9 comprises a horizontally disposed plate2| having radial arms 22, in this instance three, of such a length thatthe vertically extended ribs 23 mounted on the ends of the arms 22 clearthe periphery of the wheel l3 mounted in a horizontal position above theplate 2|, and it is to these ribs 23 that the cables 20 are secured bymeans of eye bolts 24 threaded in the upper ends of said ribs.Encircling a central perforation 25 in the plate 2| through whichloosely extends the wrench member I5, is a groove 26 of slightly greaterdiameter than a flared portion or flange 21 on the member l5 which reststherein. With this arrangement, the wrench member i5 is permitted torotate freely relative to the cradle i9, and

the groove 26 serves to maintain proper alignmentlbetween the wrenchmember l5 and the nutl slidably mounted in a groove 28 in the peripheryof the flange 21 is a support 29 for the air motor M which serves as ameans for rotating the torque producing member, or wheel l3, and isaccordingly provided with a driving connection, such as the gear 30keyed to the motor shaft 3|, which engages gear teeth 32 on the rim ofthe wheel 13. In the preferred form of the invention, the motor I4 isdesigned to reach its maximum speed, from rest, in the time required torotate the wheel I3 180 degrees. Thus, the wheel 13 reaches its maximumspeed at the instant the cams l8 engage the cams ii.

In order to .prevent the motor H from walkme, or propelling itself,around the wheel l3 when the wheel is engaged with the wrench member l5,or otherwise prevented from rotat- 'ing, a yieldable means, such as thespring 33, is

connected between the arms 34 and 35 mounted, respectively, on thewrench member I5 and the support 29. Thus, any tendency of the motor tomove relative to the wheel 13 is resisted by the nut through the memberl5-that is, rotation in this direction would tend to unscrew the nut II.This arrangement requires, of course, that nut ll be initially tightenedenough to resist this unscrewing action. The spring 33 serves, further,to reduce the shock to which the motor is subject at the instant ofimpact of the mating of cams I6 .and I 8, resulting from the tendency ofthe wrench member IE to rotate the motor support 29. However. dueto thefloating or sliding relation between the wrench member II and the motorsupport 29, at impact the spring 33 will stretch and permit the motor,as a whole, to reach an equilibrium position without rotating, relativeto the bolt I2 or other stationary objects, at the highspeed imparted tothe member I by the wheel I3. The equilibrium .position is, of course,dependent on the strength of the spring 33 and the power of themotor-that is, whenever the wheel I3 is held against rotation and themotor is supplied with power, the motor tends to travel around the wheelI3 and thereby stretch the spring 33 until the motor stalls.

As previously mentioned, the motor I4 is, in this instance, air drivenand is accordingly supplied with a motive fluid or air by means of theconduit 36 from a source (not shown). A branch 31 of the conduit 36passes through a three-way valve 38, which, for the sake of simplicity,is shown as being manually operated, and thence to the member I5 forsupplying motive fluid to the wrench for disengaging the cams I6 and I3.To this end, the wrench member I5 is provided with a central bore 39into which extends a rod or piston member 40 mounted coaxially on thewheel I3 and having a pressure surface 44 on the lower end thereofexposed to the motive fluid delivered to the lower end of the bore 39 bythe conduit 37. Thus, whenever the three-way valve 33 is positioned toallow motive fluid to flow to. the bore 39, the torque producing memberI3 will be moved vertically along its axis and thereby disengage thecams I6 and I8. The upward movement of the wheel I3 is limited by anexhaust port M for the bore 39 and positioned in such wise as to permitthe cams I6 and I8 to clear each other before the pressure fluid isexhausted from the bore 39. Reverse longitudinal, or downward, movementof the wheel I3 is attained by either exhausting the pressure fluid fromthe bore 39 through the valve 39 or by cutting of! the pressure supplyto the bore 39 by means of the valve 38 and permitting the air in thebore 39 to leak past the piston rod 40 and escape through the port 4Ithereby permitting the weight of the wheel, or gravitational force, tomove the wheel I3 into a position to align the cams I8 and I3.

Proper alignment between the wrench member I5 and the wheel I3 duringdisengagement of the cams I6 and I8 is maintained by providing a groove42 in the hub of the wheel I3 and encircling the piston member 40, intowhich flts a sleeve 43 extending from the axis of the member I5. Thelength of the sleeve 43 is of such, dimension as to permit the sleeve 43to remain in contact with the inner surface of the cams I8 at all times,and the groove 42 is of such a depth as to permit the mating faces onthe cams I6 and I8 to be in full engagement at the instant of impact.

When reverse rotation of the nut is desired, it is merely necessary toreplace the wrench member I5 with the wrench member 45 (shown in Figure4) having oppositely disposed cams 46 relative to the cams I6; mount thespring 33 and associated arms 34 and 35 on the opposite side of themotor I4, in that direction of rotation of the motor and wheel I3 arereversed; and turn over the wheel I3 so that the cams 41 provided forthis purpose on the opposite side of the wheel and having oppositelydisposed mating faces, relative to the cams I8, engage with the cams 46.There is, of course, a' piston member 40 provided on the same side ofthe wheel I3 as the cams 41, for imparting longitudinal movement to thewheel I3 for disengaging the clutch or cams 46 and 41. A protective cap43 is provided which fits over either of the members 40 and is securedthereto by bolts or screws 49 threaded through the cap 43 and extendinginto a groove 50 in the periphery of the member 40. This cap serves toprotect the end or pressure surface of the member 40 from possibledamage from an external source during the period it is not in use, i.e., when it is not inserted in the bore 39.

In operation, assuming clockwise rotation (as viewed in Fig. 2) of thewheel I3, air is valved to the motor I4 which immediately moves aroundthe periphery of the wheel l3 until the tension of the spring 33 issuflicient to stall the motor. The operator then shifts the three-wayvalve 33 to permit motive fluid to flow into the bore 39 to disengagethe cams I6 and I8, in the manner previously described. When the cams I6clear the cams I3, the three-way valve 38 is placed in position, by theoperator, to exhaust fluid from the bore 39- to permit the wheel I3 toslide into its mating position as it is rotated by the motor I4. At theinstant of impact. the wrench member I5 is fully engaged or clutched tothe wheel I3 and the kinetic or rotational energy of the wheel isdissipated in turning the nut II against frictional resistance. Theabove cycle'is then repeated until the desired tightness of the nut isattained.

Itis now obvious from the previous discussion that an impact wrenchconstructed in accordance with the practice of the invention provides arelatively simple yet highly effective means for tightening nuts andbolts and the like and which may readily be adapted for loosening thesame and, further, in both instances, torque is developed that isrelatively free of linear forces.

Still further, such a mechanism is provided with a means for preventingundue strain in any of its parts and more particularly to the primemover at the instant of impact of the cams or other clutch arrangement.

While I have shown and described a specific form of my invention, it isto be understood that various changes and modifications may be madewithout departing from the spirit of the invention as set forth in theappended claims.

I claim:

1. An impact wrench comprising, a torque producing member, means forrotating said member, means engaging the torque producing member fortransmitting rotary movement therefrom to the member to be rotated.means for disengaging the first said member from the second said means,a support for the first said means slidably mounted on the second saidmeans, and yieldable means for limiting relative movement between thesupport and the second said means. I I

2. An impact wrench comprising, a wheel shaped torque producing member,a motor for rotating said torque producing member, a driving connectionbetween the motor and the' periphery of said member, means engaging saidtorque producing member for transmitting torque therefrom to the memberto be rotated and having a chamber therein, means attached to the firstsaid member extending into said chamber and having a pressure surface onthe end there- 5 of, and means for conveying pressure fluid to saidpressure surface.

3. An impact wrench comprising, a wheel shaped torque producing member,a motor for rotating said member, a driving connection between the motorand said member, a wrench coaxial with said member for transmittingtorque therefrom to the member to be rotated and having a central bore,cams on the remote end of said wrench, cams on the first said memberengaging the first said cams, a rod attached to the first said memberand extending slidably into said bore, and means for impartinglongitudinal movement to said rod for disengaging said cams.

4. An impact wrench comprising, a wrench member having a, bore, a, wheelshaped member horizontally mounted on said wrench member and ofrelatively massive size compared to the member to be rotated, cams on anend of the wrench member, oppositely disposed cams on the wheel engagingthe first said cams, a support rotatably mounted on said wrench member,a motor mounted on the support for rotating said wheel shaped member,and yieldable means connected between said support and said wrenchmember.

5. An impact wrench comprising, a torque producing member, a wrenchadapted to be periodically engaged by such member for transmitting arotational force be a, member to be rotated, a motor slidably mounted onsaid wrench and pro-A vided with means to engage and rotate the torqueproducing member, and yieldable means yieldably connecting said wrenchto said motor for limiting rotational movement oi! the motor relative tothe torque producing member and to limit the shock, transmitted to themotor from said wrench on impact of said torque producing member withthe wrench.

FREDERIC T. HAMLIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,219,883 Amtsberg Oct. 29, 19402,285,639 Amtsberg June 9, 1942' 2,484,471 Shinn Oct. 11, 1949 FOREIGNPATENTS Number Country Date 546,372 Great Britain July 9, 1942 851,047France Sept. 25, 1939

